- Masking out SBCommandReturnObject::Printf() from the Python layer because...

- Masking out SBCommandReturnObject::Printf() from the Python layer because SWIG and varargs do not get along well.
It is replaced by a Print("str") call which is equivalent to Printf("%s","str")
- Providing file-like behavior for SBStream with appropriate extension write() and flush() calls, plus documenting that these are only meant and only exist for Python
Documenting the file-like behavior on our website

llvm-svn: 177877